Cathode active material for lithium secondary battery and lithium secondary battery including the same

ABSTRACT

A cathode active material for a lithium secondary battery according to an embodiment of the present invention includes a lithium composite oxide particle that contains lithium and transition metals including an excess amount of nickel. The lithium composite oxide particle satisfies a predetermined XRD peak area relation. A lithium secondary battery using the cathode active material and providing improved stability and durability is provided.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

This application claims priority to Korean Patent Application No.10-2020-0128489 filed on Oct. 6, 2020 in the Korean IntellectualProperty Office (KIPO), the entire disclosure of which is incorporatedby reference herein.

BACKGROUND 1. Field

The present invention relates to a cathode active material for a lithiumsecondary battery and a lithium secondary battery including the same.More particularly, the present invention relates to a cathode activematerial including a pl metal elements for a lithium secondary batteryand a lithium secondary battery including the same.

2. Description of the Related Art

A secondary battery which can be charged and discharged repeatedly hasbeen widely employed as a power source of a mobile electronic devicesuch as a camcorder, a mobile phone, a laptop computer, etc., accordingto developments of information and display technologies. The secondarybattery includes, e.g., a lithium secondary battery, a nickel-cadmiumbattery, a nickel-hydrogen battery, etc. The lithium secondary batteryis highlighted due to high operational voltage and energy density perunit weight, a high charging rate, a compact dimension, etc.

For example, the lithium secondary battery may include an electrodeassembly including a cathode, an anode and a separation layer(separator), and an electrolyte immersing the electrode assembly. Thelithium secondary battery may further include an outer case having,e.g., a pouch shape.

A lithium metal oxide may be used as an active material for a cathode ofthe lithium secondary battery. For example, the lithium metal oxide mayinclude a nickel-based lithium metal oxide. A nickel-containingprecursor compound may be used to prepare the nickel-based lithium metaloxide.

Recently, as an application range of the lithium secondary battery hasbeen expanded from a small electronic device to a large scaled devicesuch as a hybrid vehicle, a content of nickel is increasing to achievesufficient capacity and power. However, as the content of nickelincreases, reliability of the cathode active material may bedeteriorated due to mismatch and side reaction with lithium.

For example, Korean Registered Patent Publication No. 10-0821523discloses a method for manufacturing a cathode active material using alithium composite metal oxide, but still possess the problem of a highnickel-based cathode active material.

SUMMARY

According to an aspect of the present invention, there is provided acathode active material having improved stability and reliability.

According to an aspect of the present invention, there is provided alithium secondary battery having improved stability and reliability.

According to exemplary embodiments, a cathode active material for alithium secondary battery comprises a lithium composite oxide particlethat contains lithium and transition metals including an excess amountof nickel. The lithium composite oxide particle satisfies Equation 1.

1.0≤A(003)/A(104)≤1.5  [Equation 1]

In Equation 1, A(003) is an area of a peak corresponding to a (003)plane in an X-ray diffraction (XRD) analysis graph, and A(104) is anarea of a peak corresponding to a (104) plane in the XRD analysis graph.

In some embodiments, the lithium composite oxide particle may have asingle particle shape.

In some embodiments, the lithium composite oxide particle having thesingle particle shape may have a particle diameter from 3 μm to 12 μm.

In some embodiments, a spacing between (003) planes of the lithiumcomposite oxide particle may be from 100 nm to 210 nm.

In some embodiments, a full width at half maximum (FWHM) correspondingto the (003) plane in the XRD analysis graph of the lithium compositeoxide particle may be from 0.066° to 0.072°.

In some embodiments, a full width at half maximum (FWHM) correspondingto the (104) plane in the XRD analysis graph of the lithium compositeoxide particle may be from of 0.08° to 0.108°.

In some embodiments, A(003)/A(104) of the lithium composite oxideparticle may be from 1.1 to 1.4.

In some embodiments, the lithium composite oxide particle may satisfyEquation 2.

7.0≤A(104)/A(105)  [Equation 2]

In Equation 2, A(104) is the area of the peak corresponding to the (104)plane in the XRD analysis graph, and A(105) is an area of a peakcorresponding to a (105) plane in the XRD analysis graph.

In some embodiments, A(104)/A(105) of the lithium composite oxideparticle may be from 7.0 to 8.5.

In some embodiments, a reduction ratio of a specific surface area of thelithium composite oxide particle by a pressure from 2.5 ton to 3.5 tonmay be from 10% to 30%.

In some embodiments, a molar ratio of nickel in the transition metalscontained in the lithium composite oxide particle may be 0.5 or more.

In some embodiments, the transition metals of the lithium compositeoxide particle further include cobalt and manganese.

In some embodiments, the lithium composite oxide particle may berepresented by Chemical Formula 1.

Li_(x)Ni_(a)M_(1-a)O_(y)  [Chemical Formula 1]

In Chemical Formula 1, M is at least one of Al, Zr, Ti, Cr, B, Mg, Co,Mn, Ba, Si, Y, W and Sr, 0.9≤x≤1.2, 1.9≤y≤2.1 and 0.5≤a≤1.

According to exemplary embodiments, a lithium secondary battery includesa cathode including the cathode active material for a lithium secondarybattery according embodiments as described above; and an anode facingthe cathode.

In some embodiments, a reversible capacity may increase by 2% to 10% asa charging voltage increase by 0.1V based on 4.3V.

According to exemplary embodiments, a cathode active material mayinclude a lithium composite oxide in which an excess amount of nickelamong transition metals is included and a peak area ratio of a (003)plane and a (104) plane in an XRD analysis graph is within in apredetermined range.

Accordingly, stability of a crystal structure of the cathode activematerial may be improved, and durability and stability of the battery athigh temperature/voltage may be improved. Further, an amount of gasgeneration may be reduced, and penetration stability and cycle propertyof the battery may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a lithiumsecondary battery in accordance with exemplary embodiments exemplaryembodiments.

FIG. 2 is an SEM (Scanning Electron Microscopy) image of a cathodeactive material for a lithium secondary battery in accordance withexemplary embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

According to exemplary embodiments of the present invention, there isprovided a cathode active material that includes a lithium compositeoxide containing lithium and transition metals and having apredetermined range of an XRD peak ratio.

Hereinafter, the present invention will be described in detail withreference to the accompanying drawings. However, those skilled in theart will appreciate that such embodiments described with reference tothe accompanying drawings are provided to further understand the spiritof the present invention and do not limit subject matters to beprotected as disclosed in the detailed description and appended claims.

A cathode active material for a lithium secondary battery (hereinafter,may be abbreviated as a cathode active material) may include lithiumcomposite oxide particles containing lithium and a transition metalincluding an excess amount of nickel.

As used herein, the term ‘excess amount’ may refer to the largest molefraction or molar ratio.

The lithium composite oxide particle may have the largest molar fractionof nickel among transition metals.

The lithium composite oxide particle may include nickel. Nickel may beincluded in the excess amount among elements except for lithium andoxygen in the lithium composite oxide particle.

Nickel (Ni) may serve as a metal associated with a capacity of a lithiumsecondary battery. In exemplary embodiments, nickel may be included inthe excess amount of elements except for lithium and oxygen toremarkably improve the capacity of the secondary battery.

In exemplary embodiments, the molar ratio of nickel in the transitionmetal contained in the lithium composite oxide particle may be 0.5 ormore. The molar ratio of nickel among elements except for lithium andoxygen of the lithium composite oxide particles may be 0.5 or more.

Preferably, the molar ratio of nickel may be 0.6 or more, 0.7 or more,0.8 or more. Preferably, the molar ratio of nickel may be from 0.6 to0.95, from 0.7 to 0.95 or from 0.8 to 0.95.

In some embodiments, the lithium composite oxide particle may be anickel-cobalt-based lithium composite oxide further containing cobalt.In some embodiments, the lithium composite oxide particle may be anickel-cobalt-manganese (NCM)-based lithium composite oxide furtherincluding cobalt and manganese.

In exemplary embodiments, the lithium composite oxide particles may berepresented by Chemical Formula 1 below.

Li_(x)Ni_(a)M_(1-a)O_(y)  [Formula 1]

In Chemical Formula 1, M may be at least one of Al, Zr, Ti, Cr, B, Mg,Co, Mn, Ba, Si, Y, W and Sr, and 0.9≤x≤1.2, 1.9≤y≤2.1, 0.5≤a≤1.

For example, as the content of nickel increases, the capacity and powerof the lithium secondary battery may be improved. For example, nickeland manganese (Mn) may be distributed together throughout the particle,so that chemical and mechanical stability of the lithium secondarybattery may be further improved.

Manganese (Mn) may serve as a metal related to mechanical and electricalstability of the lithium secondary battery. For example, manganese maysuppress or reduce defects such as ignition and short circuit that mayoccur when a cathode is penetrated by an external object, and mayincrease a life-span of the lithium secondary electricity. Cobalt (Co)may be a metal associated with a conductivity or a resistance of thelithium secondary battery.

FIG. 2 is a scanning electron microscopy (SEM) image of a cathode activematerial for a lithium secondary battery according to exemplaryembodiments.

In exemplary embodiments, the lithium composite oxide particle may havea single particle shape as shown in FIG. 2. For example, the lithiumcomposite oxide particle may not have a secondary particle shape formedby an aggregation of a plurality of primary particles (e.g., 10 or moreprimary particles) into a substantially single unitary particle. Forexample, the single particle structure or the single particle shape mayinclude a single crystal structure (e.g., a crystal of the compound ofFormula 1).

The single particle does not exclude a form in which, for example, lessthan 10 particles are adjacent to each other and attached to each other.

In exemplary embodiments, a particle diameter (e.g., D50 from a volumecumulative distribution) of the lithium composite oxide particle may befrom 3 μm to 12 μm. If the particle diameter of the lithium compositeoxide particle is less than 3 μm, a stability of a particle surfacestructure may be reduced under high temperature or high voltageconditions, and a reactivity with the electrolyte may increase. If theparticle diameter of the lithium composite oxide particles is greaterthan 12 μm, a density of the active material layer formed of the cathodeactive material may be decreased, and a diffusivity of lithium ions maybe decreased.

The lithium composite oxide particle satisfy according to exemplaryembodiments satisfies Equation 1 below.

1.0≤A(003)/A(104)≤1.5  [Equation 1]

In Equation 1, A(003) is an area of a peak corresponding to a (003)plane in an X-ray diffraction (XRD) analysis graph, and A(104) is anarea of a peak corresponding to a (104) plane in the X-ray diffraction(XRD) analysis graph.

In exemplary embodiments, the XRD analysis may be performed in adiffraction angle (2θ) range of 10° to 120° and at a scan rate of0.01°/step using a Cu-Kα ray as a light source for a powder sample ofthe cathode active material for the lithium secondary battery.

The lithium composite oxide particle satisfying Equation 1 may haveenhanced crystallinity. In this case, physical and chemical stability ofa crystal structure may be improved. Thus, improved power and capacityof the battery may be stably maintained for a long period even duringrepeated charging and discharging operations.

Further, decomposition of the lithium composite oxide particles may beprevented under the high temperature and high voltage conditions, andthe reaction with the electrolyte may be suppressed. Therefore, highvoltage durability and high temperature storage property may beachieved.

For example, when the content of Ni in the lithium composite oxideparticle is increased, a cation disorder may occur due to an interchangeof Ni and lithium (Li), and Li ion sites may be occupied by Ni ions. Inthis case, the crystallinity of the cathode active material may bedecreased. When a temperature of a sintering process is increased toincrease the crystallinity, a desired crystal structure may not beformed due to a topotactic transition of lithium ions.

However, according to exemplary embodiments, the lithium composite oxideparticle containing the excess amount of Ni and satisfying Equation 1,the crystallinity may be improved. Accordingly, the secondary batteryhaving improved power, capacity and long-term stability may be achieved.

For example, the range represent by Equation 1 may be adjusted bychanging a type and a ratio of reactants (a composite metal precursorand a lithium source) in a manufacturing process of the cathode activematerial, or a type of gas used in the sintering process, a reactiontime, a reaction temperature, etc.

Preferably, A(003)/A(104) of the lithium composite oxide particle isfrom 1.1 to 1.4 or from 1.2 to 1.3.

In exemplary embodiments, the lithium composite oxide particle may havea spacing between the (003) planes from 100 nm to 210 nm.

In exemplary embodiments, a full width at half maximum (FWHM)corresponding to the (003) plane in the XRD analysis graph of thelithium composite oxide particle ay be from 0.066° to 0.072°.

In exemplary embodiments, an FWHM corresponding to the (104) plane inthe XRD analysis graph of the lithium composite oxide particle ay befrom 0.08° to 0.108°.

Unlike the A(003)/A(104) value, the half-width value of each peak may beinversely proportional to a crystallite size, and when a lithiumcomposite oxide having the single particle structure is included, thehalf-width value may become smaller as will be confirmed in Examples andComparative Examples to be described later.

In the above-described half-width range, the lithium composite oxideparticle may have more improved crystallinity.

In exemplary embodiments, the lithium composite oxide particle maysatisfy Equation 2 below.

7.0≤A(104)/A(105)  [Equation 2]

In Equation 2, A(104) is an area of a peak corresponding to a (104)plane in the XRD analysis graph, and A(105) is an area of a peakcorresponding to a (105) plane in the XRD analysis graph.

Preferably, A(104)/A(105) may be less than or equal to 8.5.

The lithium composite oxide particle satisfying Equation 2 may haveenhanced crystallinity. In this case, physical and chemical stability ofa crystal structure may be improved. Thus, improved power and capacityof the battery may be stably maintained for a long period even duringrepeated charging and discharging operations.

Further, decomposition of the lithium composite oxide particles may beprevented under the high temperature and high voltage conditions, andthe reaction with the electrolyte may be suppressed. Therefore, highvoltage durability and high temperature storage property may beachieved.

In exemplary embodiments, a strength of the lithium composite oxideparticle may be 500 MPa or more. If the strength is less than 500 MPa,the lithium composite oxide particle may be damaged during a highpressure rolling for forming the active material layer.

In exemplary embodiments, the lithium composite oxide particle may havea lithium-ion diffusivity of 10⁻⁸ to 10⁻⁷ S/cm under a 3.7V to 4.3Vcharge/discharge condition.

In exemplary embodiments, a specific surface area reduction ratio of thelithium composite oxide particle under a pressure from 2.5 ton to 3.5ton may be from 10% to 30%. For example, even when the lithium compositeoxide particles are rolled under the high pressure to form the activematerial layer having a density of 3.5 g/cm³ or more, a stable structureand a lithium delivery ability may be maintained.

In some embodiments, the lithium composite oxide particles may furtherinclude a coating element or a doping element. For example, the coatingelement or the doping element may include Al, Ti, Ba, Zr, Si, B, Mg, P,Sr, W, La, an alloy thereof, or an oxide thereof. These may be usedalone or in combination therefrom. The cathode active material particlemay be passivated by the coating or doping element, so that thestability relative to the external penetration and the life-span may befurther improved.

For example, the lithium composite oxide particle may be formed by areaction between a composite metal precursor and a lithium source.

The composite metal precursor may be prepared through a co-precipitationreaction of metal salts. The metal salts may include a nickel salt, amanganese salt and a cobalt salt.

Examples of the nickel salt include nickel sulfate, nickel hydroxide,nickel nitrate, nickel acetate, a hydrate thereof, etc. Examples of themanganese salt include manganese sulfate, manganese acetate, a hydratethereof, etc. Examples of the cobalt salt include cobalt sulfate, cobaltnitrate, cobalt carbonate, a hydrates thereof, etc.

The metal salts may be mixed with a precipitating agent and/or achelating agent at a ratio satisfying the content or concentration ratioof each metal described with reference to Chemical Formula 1 to form anaqueous solution. The aqueous solution may be co-precipitated in areactor to prepare the composite metal precursor.

The precipitating agent may include an alkaline compound such as sodiumhydroxide (NaOH), sodium carbonate (Na₂CO₃), or the like. The chelatingagent may include, e.g., aqueous ammonia (e.g., NH₃H₂O), ammoniumcarbonate (e.g., NH₃HCO₃), or the like.

A temperature of the co-precipitation reaction may be controlled, e.g.,in a range from about 40° C. to 60° C. A reaction time may be adjustedin a range from about 24 hours to 72 hours.

The lithium composite oxide particle (the cathode active material) maybe prepared by mixing and reacting the composite metal precursor and thelithium source. The lithium source may include, e.g., lithium carbonate,lithium nitrate, lithium acetate, lithium oxide, lithium hydroxide, etc.These may be used alone or in combination therefrom.

Thereafter, lithium impurities or unreacted precursors may be removedthrough, e.g., a washing process, and metal particles may be fixed andcrystallinity may be increased through a heat treatment (an annealing ora sintering) process.

In one embodiment, the heat treatment temperature may be in a range fromabout 600° C. to 1000° C.

According to exemplary embodiments of the present invention, a lithiumsecondary battery including the above-described cathode active materialis provided.

FIG. 1 is a schematic cross-sectional view illustrating a lithiumsecondary battery in accordance with exemplary embodiments exemplaryembodiments.

Referring to FIG. 1, the lithium secondary battery may include a cathode130, an anode 140 and a separation layer 150 interposed between thecathode and the anode.

The cathode 130 may include a cathode current collector 110 and acathode active material layer 115 formed by coating a cathode activematerial on the cathode current collector 110.

A cathode slurry may be prepared by mixing and stirring the cathodeactive material in a solvent with a binder, a conductive material and/ora dispersive agent. The cathode slurry may be coated on the cathodecurrent collector 110, and then dried and pressed to form the cathode130.

The cathode current collector 110 may include stainless-steel, nickel,aluminum, titanium, copper or an alloy thereof. Preferably, aluminum oran alloy thereof may be used.

The binder may include an organic based binder such as a polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-co-HFP),polyvinylidenefluoride (PVDF), polyacrylonitrile,polymethylmethacrylate, etc., or an aqueous based binder such asstyrene-butadiene rubber (SBR) that may be used with a thickener such ascarboxymethyl cellulose (CMC).

For example, a PVDF-based binder may be used as a cathode binder. Inthis case, an amount of the binder for forming the cathode activematerial layer may be reduced, and an amount of the cathode activematerial may be relatively increased. Thus, capacity and power of thelithium secondary battery may be further improved.

The conductive material may be added to facilitate electron mobilitybetween active material particles. For example, the conductive materialmay include a carbon-based material such as graphite, carbon black,graphene, carbon nanotube, etc., and/or a metal-based material such astin, tin oxide, titanium oxide, a perovskite material such as LaSrCoO₃or LaSrMnO₃, etc.

In exemplary embodiments, the anode 140 may include an anode currentcollector 120 and an anode active material layer 125 formed by coatingan anode active material on the anode current collector 120.

The anode active material may include a material commonly used in therelated art which may be capable of adsorbing and ejecting lithium ions.For example, a carbon-based material such as a crystalline carbon, anamorphous carbon, a carbon complex or a carbon fiber, a lithium alloy,silicon (Si)-based compound, tin, etc., may be used.

The amorphous carbon may include a hard carbon, cokes, a mesocarbonmicrobead (MCMB) fired at a temperature of 1500° C. or less, a mesophasepitch-based carbon fiber (MPCF), etc. The crystalline carbon may includea graphite-based material such as natural graphite, graphitized cokes,graphitized MCMB, graphitized MPCF, etc. The lithium alloy may furtherinclude aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin,gallium, indium, etc.

The anode current collector 120 may include, e.g., gold, stainlesssteel, nickel, aluminum, titanium, copper or an alloy thereof,preferably may include copper or a copper alloy.

In some embodiments, a slurry may be prepared by mixing and stirring theanode active material with a binder, a conductive material and/or adispersive agent in a solvent. The slurry may be coated on the anodecurrent collector 120, and then dried and pressed to form the anode 140.

The binder and the conductive agent substantially the same as or similarto those mentioned above may also be used in the anode. In someembodiments, the binder for forming the anode may include, e.g., anaqueous binder such as styrene-butadiene rubber (SBR) for compatibilitywith the carbon-based active material, and may be used together with athickener such as carboxymethyl cellulose (CMC).

The separation layer 150 may be interposed between the cathode 130 andthe anode 140. The separation layer 150 may include a porous polymerfilm prepared from, e.g., a polyolefin-based polymer such as an ethylenehomopolymer, a propylene homopolymer, an ethylene/butene copolymer, anethylene/hexene copolymer, an ethylene/methacrylate copolymer, or thelike. The separation layer 150 may also include a non-woven fabricformed from a glass fiber with a high melting point, a polyethyleneterephthalate fiber, or the like.

In some embodiments, an area and/or a volume of the anode 140 (e.g., acontact area with the separation layer 150) may be greater than that ofthe cathode 130. Thus, lithium ions generated from the cathode 130 maybe easily transferred to the anode 140 without a loss by, e.g.,precipitation or sedimentation. Thus, improvement of power and stabilitymay be efficiently realized through the combination with theabove-described cathode active material.

In exemplary embodiments, an electrode cell 160 may be defined by thecathode 130, the anode 140 and the separation layer 150, and a pluralityof the electrode cells 160 may be stacked to form an electrode assemblythat may have e.g., a jelly roll shape. For example, the electrodeassembly may be formed by winding, laminating or folding the separationlayer 150.

The electrode assembly may be accommodated together with an electrolytein an outer case 170 to define a lithium secondary battery. In exemplaryembodiments, a non-aqueous electrolyte may be used as the electrolyte.

For example, the non-aqueous electrolyte solution may include a lithiumsalt and an organic solvent. The lithium salt commonly used in theelectrolyte for the lithium secondary battery may be used, and may berepresented by Li⁺X⁻.

An anion of the lithium salt X⁻ may include, e.g., F⁻, Cl⁻, Br, I⁻, NO₃⁻, N(CN)₂ ⁻, BF₄ ⁻, ClO₄ ⁻, PF₆ ⁻, (CF₃)₂PF₄ ⁻, (CF₃)₃PF₃ ⁻, (CF₃)₄PF₂⁻, (CF₃)₅PF⁻, (CF₃)₆P⁻, CF₃SO₃ ⁻, CF₃CF₂SO₃ ⁻, (CF₃SO₂)₂N⁻, (FSO₂)₂N⁻,CF₃CF₂(CF₃)₂CO⁻, (CF₃SO₂)₂CH⁻, (SF₅)₃C⁻, (CF₃SO₂)₃C⁻, CF₃(CF₂)₇SO₃ ⁻,CF₃CO₂ ⁻, CH₃CO₂ ⁻, SCN⁻, (CF₃CF₂SO₂)₂N⁻, etc.

The organic solvent may include, e.g., propylene carbonate (PC),ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate(DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropylcarbonate, dimethyl sulfoxide, acetonitrile, dimethoxy ethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylenesulfite, tetrahydrofuran, etc. These may be used alone or in acombination thereof.

Electrode tabs may protrude from the cathode current collector 110 andthe anode electrode current collector 120 included in each electrodecell to one side of the outer case 170. The electrode tabs may be weldedtogether with the one side of the outer case 170 to form an electrodelead extending or exposed to an outside of the outer case 170.

The lithium secondary battery may be manufactured in, e.g., acylindrical shape using a can, a square shape, a pouch shape or a coinshape.

In the lithium secondary battery according to exemplary embodiments, asa charging voltage increases by 0.1V based on 4.3V, a reversiblecapacity may increase by 2% to 10%.

Hereinafter, preferred embodiments are proposed to more concretelydescribe the present invention. However, the following examples are onlygiven for illustrating the present invention and those skilled in therelated art will obviously understand that various alterations andmodifications are possible within the scope and spirit of the presentinvention. Such alterations and modifications are duly included in theappended claims.

Example 1

A lithium composite oxide particle having a single particle shape andhaving a composition of LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ with a particlesize D₅₀ of 5.5 μm from a particle size distribution analysis wasprepared as a cathode active material,

Specifically, NiSO₄, CoSO₄ and MnSO₄ were mixed in a ratio of0.5:0.2:0.3, respectively, using distilled water from which dissolvedoxygen was removed by N₂ gas bubbling. The prepared solution was putinto a reactor at 45° C., and NaOH and NH₃ H₂O were used as aprecipitating agent and a chelating agent to proceed with aco-precipitation reaction for 12 hours to obtainNi_(0.5)Co_(0.2)Mn_(0.3)(OH)₂ as a transition metal precursor. Theobtained precursor slurry was filtered and dried at 110° C. for 12hours.

Lithium hydroxide and the transition metal precursor were added in aratio of 1.05:1 in a dry high-speed mixer and uniformly mixed for 5minutes. The mixture was placed in a kiln and heated to 1,100° C. at atemperature increasing rate of 2° C./min, and maintained at 1,100° C.for 10 hours. After the sintering, natural cooling was performed to roomtemperature, followed by pulverization and classification to form thelithium-transition metal composite oxide particle having the singleparticle shape and having the composition ofLiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ composition (including single-crystal andpolycrystalline structures).

A cathode slurry was prepared by using Denka Black as a conductivematerial and PVDF as a binder, and mixing the cathode active material:the conductive material: the binder in a mass ratio of 92:5:3. Thecathode slurry was coated on an aluminum substrate, dried and pressed toform a cathode having density of 3.6 g/cc or higher.

93 wt % of an anode active material including natural graphite andartificial graphite in a 50:50 weight ratio, 5 wt % of a flake type KS6conductive material, 1 wt % of a styrene-butadiene rubber (SBR) binderand 1 wt % of carboxymethyl cellulose (CMC) as a thickener were mixed tofrom an anode slurry. The anode slurry was coated on a copper substrate,dried and pressed to prepare an anode.

The cathode and the anode obtained as described above were notched witha proper size and stacked, and a separator (polyethylene, thickness: 25μm) was interposed between the cathode and the anode to form anelectrode cell. Each tab portion of the cathode and the anode waswelded. The welded cathode/separator/anode assembly was inserted in apouch, and three sides of the pouch except for an electrolyte injectionside were sealed. The tab portions were also included in sealedportions. A non-aqueous electrolyte solution was injected through theelectrolyte injection side, and then the electrolyte injection side wasalso sealed. Subsequently, the above structure was impregnated for morethan 12 hours.

After preparing 1.0 M LiPF₆ solution in a mixed solvent of EC/EMC/DEC(25/45/30; volume ratio), 1 wt % of vinylene carbonate (VC), 0.5 wt % of1,3-propensultone (PRS) and 0.5 wt % of lithium bis(oxalato)borate(LiBOB) were added to from the electrolyte solution.

A pre-charging was performed for 36 minutes with a current (5 A)corresponding to 0.25 C. After 1 hour, degassing and aging for more than24 hours were performed, and then a formation charge and discharge wasperformed (charge condition: CC-CV 0.2 C 4.25V 0.05 C CUT-OFF, dischargecondition: CC 0.2 C 2.5V CUT-OFF).

Thereafter, a standard charging and discharging was performed (chargingcondition: CC-CV 0.5 C 4.25V 0.05 C CUT-OFF, discharging condition: CC0.5 C 2.5V CUT-OFF).

Example 2

A lithium secondary battery was manufactured by the same method as thatin Example 1, except that a lithium composite oxide having a compositionof LiNi_(0.65)Co_(0.15)Mn_(0.2)O₂ was used.

Example 3

A lithium secondary battery was manufactured by the same method as thatin Example 1, except that a lithium composite oxide having a compositionof LiNi_(0.7)Co_(0.15)Mn_(0.15)O₂ was used.

Example 4

A lithium secondary battery was manufactured by the same method as thatin Example 1, except that a lithium composite oxide having a compositionof LiNi_(0.75)Co_(0.10)Mn_(0.15)O₂ was used.

Example 5

A lithium secondary battery was manufactured by the same method as thatin Example 1, except that a lithium composite oxide having a compositionof LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂ was used.

Comparative Example 1

A lithium secondary battery was manufactured by the same method as thatin Example 1, except that a lithium composite oxide having a compositionof LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ and having a secondary particlestructure in which primary particles of small particle diameters wereaggregated was used.

Comparative Example 2

A lithium secondary battery was manufactured by the same method as thatin Comparative Example 1, except that a lithium composite oxide having acomposition of LiNi_(0.65)Co_(0.15)Mn_(0.2)O₂ was used.

Comparative Example 3

A lithium secondary battery was manufactured by the same method as thatin Comparative Example 1, except that a lithium composite oxide having acomposition of LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂ was used.

Experimental Example

(1) XRD Analysis

The lithium composite oxides of Examples and Comparative Examples wereanalyzed by an XRD (Cu-Kα ray, 2θ: 10° to 120°, scan rate: 0.01°/step).

In an analysis spectrum, a ratio of an area A(003) of a peak from a(003) plane relative to an area A(104) of a peak from a (104) plane wascalculated and shown in Table 1 below.

A ratio of an area A(104) of a peak from the (104) plane relative to anarea A(105) of a peak from a (105) plane was calculated and shown inTable 1 below.

Each peak area was calculated as an integral value of each peak.

Additionally, half widths of the peaks of the (104) plane and the (003)plane were measured and shown in Table 1 below. A unit of the half widthis degree)(°, which represents of 2θ.

(2) Evaluation on Life-Span at Room Temperature

Charging (CC-CV 1.0 C 4.25V 0.05 C CUT-OFF) and discharging (CC 1.0 C2.7V CUT-OFF) were repeated 500 times for the lithium secondarybatteries of Examples. For the secondary batteries of ComparativeExamples, charging (CC-CV 1.0 C 4.2V 0.05 C CUT-OFF) and discharging (CC1.0 C 2.7V CUT-OFF) were repeated 500 times.

A ratio of the discharge capacity at 500th cycle relative to thedischarge capacity at the first cycle was calculated as a percentage (%)to evaluate a room temperature life-span, and the results are shown inTable 1 below.

(3) Penetration Stability Evaluation

After charging the lithium secondary battery of Examples (1 C 4.25V 0.1C CUT-OFF) and charging the lithium secondary battery of ComparativeExamples (1 C 4.2V 0.1 C CUT-OFF), the batteries were penetrated by anail of 3 mm in diameter with 80 mm/sec to evaluate whether ignition orexplosion occurred by the following standard. The results are shown inTable 1 below.

<Evaluation Standard, EUCAR Hazard Level>

L1: No malfunction of battery performance

L2: Irreversible damage to battery performance

L3: A weight of the battery electrolyte was reduced by less than 50%

L4: A weight of the battery electrolyte was reduced by 50% or more.

L5: Ignition or explosion occurred.

TABLE 1 Lithium Composite Oxide Particle Capacity Molar Half Half ChargeRetention at ratio of width width A(003)/ A(104)/ Voltage roomtemperature Penetration Ni (%) (003) (104) A(104) A(105) (V) (%; @500cycles) Stability Example 1 50 0.0670 0.1077 1.24 7.23 4.25 98 L3Example 2 65 0.0687 0.1036 1.25 7.29 4.25 93 L3 Example 3 70 0.06680.0857 1.28 7.21 4.25 91 L3 Example 4 75 0.0686 0.0808 1.22 7.25 4.25 90L3 Example 5 80 0.0712 0.102 1.30 7.05 4.25 82 L3 Comparative 50 0.07090.0994 1.55 6.89 4.20 95 L3 Example 1 Comparative 65 0.0734 0.1045 1.546.72 4.20 88 L3 Example 2 Comparative 80 0.0917 0.1767 1.61 6.58 4.20 65L5 Example 3

Referring to Table 1, the cathode active materials and the lithiumsecondary batteries of Examples provided improved life-span andpenetration stability compared to those from Comparative Examplesincluding the same content of Ni.

(4) Evaluation of Gas Generation

After charging the lithium secondary battery of Examples to 100% SoC(State of Charge) (4.25V 0.05 C Cut-off), and after charging the lithiumsecondary battery of Comparative Examples to 100% SoC (4.20V 0.05 CCut-off), the batteries were stored at in a 60° C. chamber.

The lithium secondary battery was taken out from the storage chamber ateach storage period (1 week, 2 weeks, 4 weeks and 8 weeks), and anamount of gas was analyzed using a gas chromatography. The results areshown in Table 2 below.

TABLE 2 Molar Charge ratio of Voltage Gas generation amount (mL) Ni (%)(V) 1 week 2 weeks 4 weeks 8 weeks Example 1 50 4.25 3.1 3.9 5.2 7.1Example 2 65 4.25 6.0 6.8 8.4 10.8 Example 3 70 4.25 8.2 9.0 10.7 14.4Example 4 75 4.25 11.7 12 13.7 19.6 Example 5 80 4.25 12.8 13.6 16.720.5 Comparative 50 4.20 8.5 9.8 12.1 15.4 Example 1 Comparative 65 4.2013.2 14.3 17.2 20.3 Example 2 Comparative 80 4.20 18.0 19.8 23.4 35.2Example 3

Referring to Table 2, the gas generation at high temperature storage wasremarkably suppressed in the cathode active materials and the lithiumsecondary batteries of Examples provided compared to those fromComparative Examples.

What is claimed is:
 1. A cathode active material for a lithium secondarybattery comprising a lithium composite oxide particle that containslithium and transition metals including an excess amount of nickel,wherein the lithium composite oxide particle satisfies Equation 1:1.0≤A(003)/A(104)≤1.5  [Equation 1] wherein, in Equation 1, A(003) is anarea of a peak corresponding to a (003) plane in an X-ray diffraction(XRD) analysis graph, and A(104) is an area of a peak corresponding to a(104) plane in the XRD analysis graph.
 2. The cathode active materialfor a lithium secondary battery of claim 1, wherein the lithiumcomposite oxide particle has a single particle shape.
 3. The cathodeactive material for a lithium secondary battery of claim 2, wherein thelithium composite oxide particle having the single particle shape has aparticle diameter from 3 μm to 12 μm.
 4. The cathode active material fora lithium secondary battery of claim 1, wherein a spacing between (003)planes of the lithium composite oxide particle is from 100 nm to 210 nm.5. The cathode active material for a lithium secondary battery of claim1, wherein a full width at half maximum (FWHM) corresponding to the(003) plane in the XRD analysis graph of the lithium composite oxideparticle is from 0.066° to 0.072°.
 6. The cathode active material for alithium secondary battery of claim 1, wherein a full width at halfmaximum (FWHM) corresponding to the (104) plane in the XRD analysisgraph of the lithium composite oxide particle is from of 0.08° to0.108°.
 7. The cathode active material for a lithium secondary batteryof claim 1, wherein A(003)/A(104) of the lithium composite oxideparticle is from 1.1 to 1.4.
 8. The cathode active material for alithium secondary battery of claim 1, wherein the lithium compositeoxide particle satisfies Equation 2:7.0≤A(104)/A(105)  [Equation 2] wherein, in Equation 2, A(104) is thearea of the peak corresponding to the (104) plane in the XRD analysisgraph, and A(105) is an area of a peak corresponding to a (105) plane inthe XRD analysis graph.
 9. The cathode active material for a lithiumsecondary battery of claim 8, wherein A(104)/A(105) of the lithiumcomposite oxide particle is from 7.0 to 8.5.
 10. The cathode activematerial for a lithium secondary battery of claim 1, wherein a reductionratio of a specific surface area of the lithium composite oxide particleby a pressure from 2.5 tons to 3.5 tons is from 10% to 30%.
 11. Thecathode active material for a lithium secondary battery of claim 1,wherein a molar ratio of nickel in the transition metals contained inthe lithium composite oxide particle is 0.5 or more.
 12. The cathodeactive material for a lithium secondary battery of claim 1, wherein thetransition metals of the lithium composite oxide particle furtherinclude cobalt and manganese.
 13. The cathode active material for alithium secondary battery of claim 1, wherein the lithium compositeoxide particle are represented by Chemical Formula 1:Li_(x)Ni_(a)M_(1-a)O_(y)  [Chemical Formula 1] wherein, in ChemicalFormula 1, M is at least one of Al, Zr, Ti, Cr, B, Mg, Co, Mn, Ba, Si,Y, W and Sr, 0.9≤x≤1.2, 1.9≤y≤2.1 and 0.5≤a≤1.
 14. A lithium secondarybattery, comprising: a cathode comprising the cathode active materialfor a lithium secondary battery of claim 1; and an anode facing thecathode.
 15. The lithium secondary battery of claim 14, wherein areversible capacity increases by 2% to 10% as a charging voltageincreases by 0.1V based on 4.3V.